Six systems, side by side
Each row maps one test's labels from IQ 40 to 170. The line marks your score and the highlight shows that test's name for the band. Hover for its range.
WAIS-IV (2008) used 10-point bands around 100, including 'Borderline' for 70–79 and 'Very superior' from 130.
Its manual treats those words as score labels, to be read alongside the confidence interval, not descriptions of a person.
Source check, October 2026: Wechsler-Bellevue ranges and shares (128+ = 2.2%, 120–127 = 6.7%, 111–119 = 16.1%) follow Wechsler's Measurement of Adult Intelligence. WAIS-IV, SB5 and Terman ranges were checked against their standard tables; DSM-IV categories are approximate and deliberately overlap.
Ratio IQ broke for adults; the deviation IQ fixed it
Terman divided mental age by real age. Fine for children, whose performance climbs every year. Adult performance levels off in the late teens, so dividing a flat mental age by a rising real age makes every adult look like they are declining. Terman's workaround was to stop the divisor at 16.
Wechsler dropped the ratio altogether. A deviation IQ ranks you against people your own age, so a 40-year-old and a 9-year-old with IQ 115 are both one SD above their peers. Every modern band is set on that footing.
How likely is IQ 128 to belong in each WAIS-IV band?
Every score carries error. A full-scale Wechsler sits around 2 to 3 points of standard error, short screeners and online tests nearer 5 or worse. Land close to a band edge and the honest label is "probably X, possibly Y", which is what the confidence interval in a report is for. The good reports name both bands when that interval crosses a line.
Clinical terms that became insults, and what replaced them
Listed for history only. Current systems (DSM-5, ICD-11) define intellectual disability by both measured ability and adaptive functioning, and grade severity mainly on adaptive functioning.
"Gifted" has no single line
Schools write their own entry rules. Most land around 120 to 130, or a percentile, and many weigh achievement scores or teacher ratings alongside it. Miraca Gross's labels for the range past 130 are widely used, but almost no test measures that far out with real precision.
Three decisions that need more than a score
A result of 68 tells a clinician to look closer; it does not settle a diagnosis. A 72 does not settle the question either.
The local school or district writes the entry rule. A label on a score report is seldom the whole answer.
Today, assessors look at a person's response to focused teaching as well as test scores, not just an IQ–achievement gap.
- Terman, L. M. (1916). The Measurement of Intelligence. Houghton Mifflin.
- Wechsler, D. (1939). The Measurement of Adult Intelligence. Williams & Wilkins.
- Roid, G. H. (2003). Stanford-Binet Intelligence Scales, Fifth Edition: Technical Manual. Riverside.
- Wechsler, D. (2008, 2014). WAIS-IV and WISC-V Technical and Interpretive Manuals. Pearson.
- American Psychiatric Association (1994; 2013). DSM-IV and DSM-5.
- Gross, M. U. M. (2004). Exceptionally Gifted Children (2nd ed.). RoutledgeFalmer.
- Rosa's Law, Pub. L. 111-256 (2010).
- World Health Organization (2019/2022). ICD-11: Disorders of intellectual development (6A00).
- Schalock, R. L., Luckasson, R., & Tassé, M. J. (2021). Intellectual Disability: Definition, Diagnosis, Classification, and Systems of Supports (12th ed.). AAIDD.